The term was coined by several people in the Alt+H Discord server in January 2018. 
"'Otherlink' is a word that was coined in discussions of voluntary identities that weren’t constructed or chosen strictly for coping reasons, or for those who felt like the ‘coping’ part of the name undermined the identity or “broke the immersion” of some of it, so to speak.
So it’s a more generalized form of “copinglink,” in short. One that includes copinglinks but doesn’t necessitate that an identity be a coping-based one." - Victim of Changes, 26 January 2018 
See everything tagged #otherlink by Victim of Changes http://victiim-of-changes.tumblr.com/tagged/otherlink
- ↑ Victim of Changes "Otherlinkers are not "'kin but Voluntary"" January 26, 2018 http://victiim-of-changes.tumblr.com/post/170162038800/otherlinkers-are-not-kin-but-voluntary (Archived March 25, 2018 https://web.archive.org/web/20180325235532/http://victiim-of-changes.tumblr.com/post/170162038800/otherlinkers-are-not-kin-but-voluntary )
- ↑ February 5, 2018 http://victiim-of-changes.tumblr.com/post/170561701235/ey-is-there-a-word-for-voluntary-identity-that (Archived March 26 2018 at https://web.archive.org/web/20180326001232/http://victiim-of-changes.tumblr.com/post/170561701235/ey-is-there-a-word-for-voluntary-identity-that )
- ↑ http://victiim-of-changes.tumblr.com/post/170170259665/question-is-this-term-synonymous-with-copinglink ( Archived March 26, 2018 at https://web.archive.org/web/20180326001942/http://victiim-of-changes.tumblr.com/post/170170259665/question-is-this-term-synonymous-with-copinglink )